In phase three of both 10 and 25 man Onyxia (read all about it here), you will find yourself being regularly feared. The floor will also be exploding. My advice had been simply to “try not to stand on the cracks of the floor”, however there is a nifty little space I found that you can stand on and avoid any floor damage, as well as any possibility of being feared into a whelp cave.
During this phase, you can jump up onto a ledge (approximately where the red arrow is pointing) which will put you above the level of the exploding floor. When you get feared, you’ll run along the red oval, never having to worry about running toward the whelps while you can’t control your movement :)